Multiple filament electric lamp



Feb. 6, 1934. w DAWSQN 1,946,393

MULTIPLE FILAMEN'I' ELECTRIC LAMP Filed Dec. 14, 1932 Fig.1. 6

/N VE N TOR Patented F ch. 6, 1934 MULTIPLE FILAMENT ELECTRIC LAMP Wilfred Dawson, Golders Green, London, England Application December 14, 1932, Serial No. 647,235, and in Great Britain December 18, 1931 6 Glaims.

This invention relates to electric lamps of the multiple filament type.

The object of the invention is to provide a lamp cap having improved means whereby the difierent filaments of the lamp may be selectively brought into circuit while retaining the standard forms of lamp holder.

provide a detachable cap portion for a multiple filament lamp which has two contact arms for making contact with the leading-in wires of the lamp. It is also an object of the invention so to form these contact arms that, whilst emcient to maintain good contact, they do not hinder the attachment of the cap to the rest of the lamp.

With these and other objects in view, the invention resides in certain novel features of construction and combination of parts which will be more fully hereinafter described and pointed out in the claims.

Referring to the accompanying drawing which illustrates the invention in a diagrammatic manner- Figure 1 represents in elevation, partly in section, the upper or cap portion of a three filament lamp constructed in a preferred manner according to the invention for a bayonet type of fitting.

Figure 2 shows a plan view of the contact ring,

Figure 3 shows a cross-section through the detached upper portion of the cap.

Figure 4 shows a cross-section through the contact ring to an enlarged scale.

Referring to the drawing, the cap comprises an upper part A, preferably of metal, provided with the usual bayonet pins 0. and contact studs b, c. The lower portion A of the part A is of larger diameter than the upper portion and is a close fit upon a lower metal sleeve Bsecured to the lamp bulb C.

Suitable means such as snap groove d is provided to cause the parts A and B to be held tightly together.

The part A has cut-away part D at its bottom for a portion of its circumference. A pin ,f carried by the sleeve B projects through this cut-away portion and on the part A being turned relatively to the sleeve B this cut away portion limits the amount of angular movement.

The part A is provided with a small recess e and the part B with three similar projections one corresponding to each end of the portion D and one to the centre thereof so that a click efiect for the three operative relative positions of the parts A and B is provided. The sleeve B is provided with a shoulder g which serves as an end guide for the member A.

A contact ring E of insulating material is secured in the sleeve B a short distance'below the shoulder g; this ring has secured therein in its inner circumference three short metallic contact pieces F and a long contact piece G. Axial holes are provided in the ring near the centre of each contact piece and short metal tubes h, connected to the contact pieces, are housed in the holes.

The ring E may conveniently be made of a plastic artificial resin such as bakelite and the contact pieces with their tubes can be moulded therein with the contact parts projecting slight- 1y from the ring.

Instead of tubes 71. small castings or stampings to form the contact pieces may be used, these castings having holes through them for the wires.

The common lead wire J, Figure 4, is passed through the hole in the tube connected to the contact piece G and may be soldered at the top, and the lead wires are passed through the other tubes and may be similarly soldered.

Contact arms a, k'project from the top A, one being electrically connected to the contact stud b and the other is to the contact stud c.

7 These arms of springy material and preferably of U or V section as shown in Figure 2, and are so shaped that one makes contact with the long contact piece G while the other makes selective contact with one of the contact pieces F on the inner surface of the ring E.

The recess e and the similar projections on the part B are so placed that they click when the arm is in central contact with one of the contact pieces F and the other contact piece G is made of such length that the arm it makes contact with it throughout the range of its movement.

With this construction the top portion A of the cap is detachable from the remainder of the cap and can be used again.

The lower ends of the arms a, k are bent slightly inwards as shown in Figure 3; this ensures that, when the top portion is inserted, these arms will be guided into the inner surface of the ring E.

It will be noted that the depth of the contact pieces F, G and the shape of the arms a, k is such that effective contact will be ensured even if there is slight variation in manufacture in difierent caps in the depth of the ring E in relation to the snap groove d or in the depth of the top portion A.

Instead of the cut-away portion D I may provide a slot, or alternatively I may provide the means for limiting the relative angular movement of the sleeves entirely within the cap, for instance by forming projections on the ends of the long contact G to limit the angular movement or" the arm k.

In most cases it is sufiicient to rely upon the springy nature of the arms 7', lo to ensure efiective contact, but if desired they may be positively pressed apart by separate spring means which must of course, be so arranged that the contact making arms are insulated from each other.

The parts A, B are shown as made of metal but they may be formed of mouldable artificial resin.

Other modifications in detail may be effected, coming within the ambit of the claims which follow.

Reference is made to companion case 647,234 of even date, which case is for similar subject matter shown but not claimed in this application.

I claim:-

1. A multiple filament electric lamp comprising a bulb portion having a leading-in wire common to all its filaments and a leading-in wire particular to each of the filaments, and a cap capable of detachment from said bulb portion and having a contact arm adapted at all times when the cap and bulb are in assembled relation to make contact with said common leading-in wire and a contact arm adapted upon relative movement between said bulb and said cap to make selective contact with each of said other leading-in Wires, and means for limiting the relative movement between said bulb and said cap.

2. A multiple filament electric lamp comprising a cylindrical cap portion fixed to the bulb portion of the lamp, said cap having an exposed concave surface, a cap portion movable relatively thereto and detachable therefrom, contact pieces carried upon the concave surface of said first cap portion and connected respectively to the leading-in wire common to all the filaments or the lamp and to the leading-in wires particular to each of the filaments, a contact arm carried by said detachable cap portion, and adapted at all times when said cap portions are in assembled relation to make contact with that one of the said contact pieces which is connected to the common leadingin wire, and a second contact arm carried by said detachable cap portion and adapted upon relative movement of said cap portions to make selective contact with the contact pieces connected to the leading-in Wires particular to the individual filaments.

3. A multiple filament electric lamp comprising a bulb portion, a ring of insulating material carried by said bulb portion, contact pieces arranged on the inner surface of said ring and connected respectively to a leading-in wire common to all the filaments of the lamp and to leading-in wires particular to each of the filaments, a cap, a contact arm carried by said cap and adapted to make contact with the contact piece connectedto the common leading-in wire, and a second contact arm carried by said cap and adapted upon relative movement between said cap and said bulb to make selective contact with the other of said contact pieces.

4. A multiple filament electric lamp comprising a bulb portion, a ring of insulating material carried by said bulb portion, contact pieces arranged on the inner surface of said ring, tubes of electrical conducting material passing through said ring, each of said tubes being connected to one of said contact pieces and receiving a leadingin wire of the lamp, a cap capable of detachment from said bulb portion and carrying two contact arms, one of said arms being adapted at all times when the cap and bulb are in assembled relation to make contact with that one of the said contact pieces which is connected to the common leading-in wire of the lamp, and the other of said arms being adapted upon relative movement between said cap and said bulb to make selective contact with the other contact pieces.

5. For use with a multiple filament electric light bulb having a leading-in wire common to all its filaments and a leading-in wire particular-to each or" the filaments, a cap comprising means to attach it to the bulb, a contact arm adapted at all times to make contact with the common leading-in wire and a second contact arm adapted upon relative movement between the said cap and bulb to make selective contact with each of the other leading-in wires, and means for limiting the relative movement between said bulb and said cap.

6. For use with a multiple filament electric light bulb having a leading-in wire common to all its filaments and a leading-in wire particular to each of the filaments, contact terminals for all of said leads, a cap comprising means to attach it to the bulb, a contact arm adapted at all times to make contact with the common leading-in wire and contact terminal and a second contact arm adapted upon relative movement between the said cap and bulb to make selective contact with each of the other leading-in wires, said contact arms being resiliently constructed and curved inwardly at their ends to facilitate their insertion into the bulb portion of the lamp.

WILFRED DAWSON. 

